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Tech Ingredients on Youtube did an interesting video about actively air-cooling panels. In the video he uses 3 watts of fans to cool a 100 watt panel, which in

Tech Ingredients on Youtube did an interesting video about actively air-cooling panels. In the video he uses 3 watts of fans to cool a 100 watt panel, which increases its output by 6 watts. The gains are modest (~5%), but his argument is that the lower operating temp will increase the longevity of the panels, which should make the ROI positive. I'm sure the designers of the panels could engineer more efficient solutions. It did get me wondering about the importance of the roof underneath the panels. Most people install black panels over top black asphalt shingles for aesthetic reasons, but I wonder if some other variation would increase efficiency and/or longevity. https://www.youtube.com/watch?v=Mt9qLRN7JvA https://www.youtube.com/watch?v=Mt9qLRN7JvA

Scoundreller 3y ago
Looks like you beat me to it by a minute, but worth pointing out those numbers were at around 60w of output. The difference probably increases at full output.
Freestyler_3 3y ago
White background with double sided panels.
pengaru 3y ago
You could configure the installation to create a natural convection current of air traveling between the panels and the roof deck, so no power wasted at all on the "fan". Then you could take it a step further by running some "earth tubes" up to the low/entry point of this cooling channel, so the incoming air for the convection current is cooler. All passive.
- friend_and_foe 3y ago
  This is similar to my plan. I plan to cool and warm my house using an earth tube or two, which leaves electricity required for very modest use, lighting, charging phones and what not and a refrigerator. Combined with a white or silver metal roof and a good gap between the solar panels to allow wind to flow through in leu of an attic should do me just fine, and on top of that the inside air will always be fresh from outside. The energy saving will be tremendous, and digging a trench for the earth tubes will actually cost less than installing a central air conditioning unit. Additionally you don't really need insulation, since fresh temperate air is always cycling in and is available pretty much endlessly, the limiting factor on efficiency is air flow, not insulation. Also, no condensation in the walls; they'll always be above the dew point in the summer, and in the winter the air will be well below 100% relative humidity since the ambient air is being warmed, not cooled, and so the walls will never be below the outside ambient temperature in the winter. The only downsides I can see are that I can't set the temperature, it would be whatever it is in the ground, which at the right depth should be around 73F year round, and 100% relative humidity in the summer. That and that the house must be designed for maximum air flow but I don't really see that as a downside, people have designed houses this way forever until the advent of air conditioning, and to be honest I'm not a fan of a house design that doesn't take air flow into consideration.
  - pengaru 3y ago
    I don't think earth tubes are ideal for such direct plumbing into living spaces. My understanding is that they tend to develop mold and stagnant moisture will pool in the underground portion. Imagine a hot and humid day, the humid air will condense on the cool walls while passing through the underground section of the tube. Do you really want that to be your fresh air duct? But it seems like a useful mechanism for delivering ground-coupled outdoor air to an outdoor application, which could be a heat exchanger participating in regulating indoor temperatures.
    - friend_and_foe 3y ago
      Yes, my design right now includes a HEPA filter on the intake, preventing spores from ever even getting in the tube, a slight grade downwards towards the intake and a water catchment system at the end with a float tank activated pump to pump the water out periodically.
      - pengaru 3y ago
        I'd love to hear how that plays out after a decade of use. It's something I've considered experimenting with for a future ADU/guest-house on my desert property, but it seems too troublesome for my liking.
        friend_and_foe 3y ago
        Yeah it sounds troublesome at first, but then you realize that digging a trench and laying some pipe is cheaper, easier and less maintenance than having a machine with moving parts and duct work and all that. In a desert I'm guessing in north america, the only things you have to consider are that the ground may be very rocky and also the pipe won't be in wet soil which will mean it will cool less quickly and you have to run a longer pipe. The good side is you're not likely to have tree roots crack the pipe and youre very likely to keep the humidity well below 100% even in the summer. I'd say go for it, deserts are very mold free. You might also consider radiative cooling with some of that super white paint that radiates heat faster than it collects, since you'll have less shadows and clouds it should radiate rather well, downside being colder nights and winters.
- PaulKeeble 3y ago
  This is why the panels are raised off he roof with racking. Its allows the air to flow underneath them to cool them. The issue with heating is you have a mostly black object getting ~1400Watts/m^2 and just 20% of it is turned into electricity and the rest is heating the panel. Its a lot of heat.
  - garyclarke27 3y ago
    True Black objects get incredibly hot in the sun I've long thought that Solar Panel should be combined with Thermoelectric generator but I guess the economics don't stack up yet. Thermoelectric is not very efficient and progress is painfully slow.
    - adrianN 3y ago
      For thermoelectric generators you need a cool side. Where would you get that?
dymk 3y ago
Still not worth it aside from the "neat" factor. 3 watts net increase won't pay for the cost of the fan over the lifetime of the panel, and a moving part like a fan won't make it to 25 years (5 years if it's lucky).
- byyll 3y ago
  Many people run Noctua fans for more than 10 years.
  - dymk 3y ago
    Sure, in a PC case. Not outside exposed to the elements.
    - Scoundreller 3y ago
      Presumably the fan isn’t really exposed to much other than atmospheric air at atmospheric. There’s generally Less dust outside than inside. I’m doubting humidity has much effect on fans. I suspect biggest failure mode for fans are the bearing’s lubrication drying out. Sometimes this can be serviced (with much difficulty) or take the efficiency hit and use a thicker grease that doesn’t evaporate as fast. Nice thing is that they’re not a critical part here, and it’s diminishing returns so if you have multiples and 1 fails, you’re still ok.
      - evilos 3y ago
        The combined heat and humidity cycles of being on a roof would be quite damaging to any electro-mechanical machine. Especially one that isn't designed for that kind of environment. I'd be surprised if a PC fan made it more than 2 or 3 years in that environment. Probably depends a lot on the specific climate though.
  - PaulKeeble 3y ago
    25 years in all weather, not even a Noctua fan is making it that long. Its not the cost of the panels that is the issue its getting them on the roof, repairing them is enormously expensive as they have no gaps between them and buying replacements a decade later is almost impossible as people are finding out. Longevity to maximise returns is a necessity with an investment that takes 7 years to break even.

Scoundreller 3y ago

Looks like you beat me to it by a minute, but worth pointing out those numbers were at around 60w of output. The difference probably increases at full output.

Freestyler_3 3y ago

White background with double sided panels.

pengaru 3y ago

You could configure the installation to create a natural convection current of air traveling between the panels and the roof deck, so no power wasted at all on the "fan". Then you could take it a step further by running some "earth tubes" up to the low/entry point of this cooling channel, so the incoming air for the convection current is cooler. All passive.

friend_and_foe 3y ago
This is similar to my plan. I plan to cool and warm my house using an earth tube or two, which leaves electricity required for very modest use, lighting, charging phones and what not and a refrigerator. Combined with a white or silver metal roof and a good gap between the solar panels to allow wind to flow through in leu of an attic should do me just fine, and on top of that the inside air will always be fresh from outside. The energy saving will be tremendous, and digging a trench for the earth tubes will actually cost less than installing a central air conditioning unit. Additionally you don't really need insulation, since fresh temperate air is always cycling in and is available pretty much endlessly, the limiting factor on efficiency is air flow, not insulation. Also, no condensation in the walls; they'll always be above the dew point in the summer, and in the winter the air will be well below 100% relative humidity since the ambient air is being warmed, not cooled, and so the walls will never be below the outside ambient temperature in the winter. The only downsides I can see are that I can't set the temperature, it would be whatever it is in the ground, which at the right depth should be around 73F year round, and 100% relative humidity in the summer. That and that the house must be designed for maximum air flow but I don't really see that as a downside, people have designed houses this way forever until the advent of air conditioning, and to be honest I'm not a fan of a house design that doesn't take air flow into consideration.
- pengaru 3y ago
  I don't think earth tubes are ideal for such direct plumbing into living spaces. My understanding is that they tend to develop mold and stagnant moisture will pool in the underground portion. Imagine a hot and humid day, the humid air will condense on the cool walls while passing through the underground section of the tube. Do you really want that to be your fresh air duct? But it seems like a useful mechanism for delivering ground-coupled outdoor air to an outdoor application, which could be a heat exchanger participating in regulating indoor temperatures.
  - friend_and_foe 3y ago
    Yes, my design right now includes a HEPA filter on the intake, preventing spores from ever even getting in the tube, a slight grade downwards towards the intake and a water catchment system at the end with a float tank activated pump to pump the water out periodically.
    - pengaru 3y ago
      I'd love to hear how that plays out after a decade of use. It's something I've considered experimenting with for a future ADU/guest-house on my desert property, but it seems too troublesome for my liking.
      - friend_and_foe 3y ago
        Yeah it sounds troublesome at first, but then you realize that digging a trench and laying some pipe is cheaper, easier and less maintenance than having a machine with moving parts and duct work and all that. In a desert I'm guessing in north america, the only things you have to consider are that the ground may be very rocky and also the pipe won't be in wet soil which will mean it will cool less quickly and you have to run a longer pipe. The good side is you're not likely to have tree roots crack the pipe and youre very likely to keep the humidity well below 100% even in the summer. I'd say go for it, deserts are very mold free. You might also consider radiative cooling with some of that super white paint that radiates heat faster than it collects, since you'll have less shadows and clouds it should radiate rather well, downside being colder nights and winters.
PaulKeeble 3y ago
This is why the panels are raised off he roof with racking. Its allows the air to flow underneath them to cool them. The issue with heating is you have a mostly black object getting ~1400Watts/m^2 and just 20% of it is turned into electricity and the rest is heating the panel. Its a lot of heat.
- garyclarke27 3y ago
  True Black objects get incredibly hot in the sun I've long thought that Solar Panel should be combined with Thermoelectric generator but I guess the economics don't stack up yet. Thermoelectric is not very efficient and progress is painfully slow.
  - adrianN 3y ago
    For thermoelectric generators you need a cool side. Where would you get that?

dymk 3y ago

Still not worth it aside from the "neat" factor. 3 watts net increase won't pay for the cost of the fan over the lifetime of the panel, and a moving part like a fan won't make it to 25 years (5 years if it's lucky).

byyll 3y ago
Many people run Noctua fans for more than 10 years.
- dymk 3y ago
  Sure, in a PC case. Not outside exposed to the elements.
  - Scoundreller 3y ago
    Presumably the fan isn’t really exposed to much other than atmospheric air at atmospheric. There’s generally Less dust outside than inside. I’m doubting humidity has much effect on fans. I suspect biggest failure mode for fans are the bearing’s lubrication drying out. Sometimes this can be serviced (with much difficulty) or take the efficiency hit and use a thicker grease that doesn’t evaporate as fast. Nice thing is that they’re not a critical part here, and it’s diminishing returns so if you have multiples and 1 fails, you’re still ok.
    - evilos 3y ago
      The combined heat and humidity cycles of being on a roof would be quite damaging to any electro-mechanical machine. Especially one that isn't designed for that kind of environment. I'd be surprised if a PC fan made it more than 2 or 3 years in that environment. Probably depends a lot on the specific climate though.
- PaulKeeble 3y ago
  25 years in all weather, not even a Noctua fan is making it that long. Its not the cost of the panels that is the issue its getting them on the roof, repairing them is enormously expensive as they have no gaps between them and buying replacements a decade later is almost impossible as people are finding out. Longevity to maximise returns is a necessity with an investment that takes 7 years to break even.